Sure, you can use a self-signed cert, if you don't mind going through the process of installing the cert into every browser that you'll use to access the server.

But Sandstorm is designed for sharing and collaboration. For example, you might write a document in Etherpad which you want other people to comment on. It may be tough to get the right certificate into all your friends' and family's browsers.

(Note that Sandstorm actually provides free wildcard certificates if you are OK with using a subdomain of sandcats.io.)